Kinetic analysis of palladium(II) adsorption process on condensed-tannin gel based on redox reaction models.
Kinetic analysis of palladium(II) adsorption process on condensed-tannin gel based on redox reaction models.
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DOI：
10.1016/j.watres.2007.02.016
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发表时间：
2007-07
期刊：
影响因子：
12.8
通讯作者：
Y. Kim;Takeshi Ogata;Y. Nakano
中科院分区：
文献类型：
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作者：
Y. Kim;Takeshi Ogata;Y. Nakano
我们开发了一种新型回收系统，利用由缩合单宁分子合成的单宁凝胶颗粒，从废催化剂或废料等废物中回收钯 (Pd)。 Pd(II) 离子在单宁凝胶网络上被还原为金属 Pd(0)：从单宁凝胶到 Pd(II) 的双电子转移。电子转移动力学研究采用包含中间步骤（形成配体取代的Pd(II)-单宁内球络合物）的多反应模型进行，与单反应模型（外球氧化还原反应）相比，与实验结果更加吻合，这意味着内球氧化还原机制是Pd(II)吸附过程的合适反应模型。由于中间体包含在吸附量中，吸附过程可分为两步：初始阶段通过配体取代进行快速吸附，以及配体取代达到平衡状态后通过后续氧化还原反应进行缓慢吸附，Pd(II)离子种类之间的吸附速率不同（PdCl+>PdCl2>PdCl3-、PdCl42-）。
We have developed a novel recovery system of palladium (Pd) from wastes such as spent catalysts or scraps, using tannin gel particles synthesized from condensed-tannin molecules. The Pd(II) ionic species are reduced to metallic Pd(0) on the network of the tannin gel: a two-electron transfer from the tannin gel to Pd(II). The kinetic study of the electron transfer was performed with a multiple reaction model containing an intermediate step (formation of a ligand-substituted Pd(II)–tannin inner sphere complex), resulting in a better fit with the experimental results than with the single reaction model (outer sphere redox reaction), which means that the inner sphere redox mechanism is an appropriate reaction model for the Pd(II) adsorption process. Because the intermediate is included in the adsorption amount, the adsorption process can be divided into two steps: fast adsorption by the ligand substitution at the initial stage and slow adsorption by the subsequent redox reaction after the ligand substitution reaches an equilibrium state, with different adsorption rates between the Pd(II) ionic species (PdCl+>PdCl2>PdCl3-,PdCl42-).